Coil



H. WHlTTLE Feb. 7, 1933.

COIL

Filed Dec. 51, 1930 INVENTOR H.WH/TTLE BY J l Aria/wry such a coil often has impressed Patented Feb. 7, 1 933 7 UNITED, STATES- PATENT oFFica HORACE WHITTLE, OF mmzwoon, NEW JERSEY, ASSIGNOR TO BELL TELEPHONE LABORATORIES, IIICORPORATED, YORK OF NEW YORK, N. Y., A CORPORATION OI NEW Application filed December 81, 1930. Serial No. 505,798.

ditions and over a great range of current densities.- .For example, such a coil must repeat eifectively the minute currents due to speech, the somewhat larger but yet small currents due to ringing or signaling currents arriving over a very long line, and the rela-' tively large ringing or signaling currents arriving over a very short line. In addition, upon it for long or short periods of time various amplitudes of direct continuous voltage as well as of impulsive disturbances etc. When limitations of cost and size are imposed the problem of designing a coil to meet the required conditions is one of .increased difliculty. Furthermore, a coilonce installed must continue to function efiectively over a long pe'- riod of time without maintenance, although subjected numberless times to thervarious .large and small voltages incident to its operation. It is primarily to. such repeating coils that the present invention relates.

Prior to the present invention there have 11 proposed for use in telephone repeating coil and other cores two suitably selected mag netic materials in'parallel. A transformer having such a core, when properly designed, will have the range of ,its' effectiveness increased. Such devices attain, to a degree, the objects of the present invention. In accordance with a feature of the present invention, further improvements are efiected by the use in one core of new combinations of magnetic materials suitable for the production of coils of special properties.

. type having an treated in a loy of from In accordance with another feature, cores are made of three or more materials each different from the others and each selected with the properties of the others taken into consideration to effect an improved result.

l/Vhen only two materials them is an alloy of cobalt and iron/of the unusually high flux density at high magnetizing forces and especially a known: variety of cobalt-iron alloy composed of around 40% to 60% iron and 60% to 40% cobalt which has a high permeability in the range of magnetizing forces around 3 to 6 games and upward. However, other cobalt-iron alloys, especially those in the range 40 to 70% iron, may be employed. Alloys of cobalt and 50% iron when heat best magnetic properties, as previously de scribed by another, are preferred. Within the scope of the term cobalt-iron are included certain recently developed magnetic materials which consist essentially of cobalt and iron with additional substances added to make them more readily workable.

' The second magnetic material, when two are employed, may consist of silicon steel of a good commercialgrade or a nickel-iron aldevelop high permeability in a low range of magnetizing forces. The number of rings or laminations of the second material will usually'be equal to the number of the first material, but may be more or less, as preferred.

When a' third magnetic material is employed it will preferabl consist of one of the varieties of iron-nicke, alloy having chromium, molybdenum or other equivalent material added to increase the permeability in an extremely low range of magnetizing forces near zero and to decrease the residual magnetism and coercive force. Such materials comprise, for example, 45 to 85% nickel, 2. to 10% chromium or molybdenum and the balance iron, heat treated in a manner previous ly described by another to develop the mag-' netic properties just stated. A composition of about 5% nickel, 3 to 4% chromium and the balance iron is quite suitable. Such added are used one of manner suitable to develop their 40 to 85% nickel, heat treated to materials,- chromium, for example, modify both the magnetic and resistive properties of the material. For convenience they may be referred to as resistivity increasing materials;

For constructing the core of a telephone ringing transformer it is generally preferred that the number of laminations of the third magnetic material be smaller in number than of the first two materials. Thus the addition of a few laminations of 75% 21 3 70 nickel-iron-chromium alloy not only serves to increase the effective permeability of the core at low flux densities approaching zero but also stabilizes the permeability of the core at magnetizing forces resulting from currents of the intensity and frequency of voice currents after being subjected to the magnetizing forces resulting from the application of heavy ringing or signaling currents to the circuit including the coil Winding.

Such cores as described can perform the same variety of a single'core material and although the cost of the cobalt is relatively high the sav-- ings in copper and space may be more than suflicient to offset the higher cost of the core material. They are alsocapable of being-designed to' perform more satisfactorily than other cores of two materials heretofore de-' scribed.

Anembodiment of the present invention is illustrated in the accompanying drawing in which: a i

The figure represents,. in a 'semi-diagram-- matic manner, a repeating coil having primary and secondary windings, the core of the coil consisting of alternate layers or laminations of cobalt-iron and high permeability nickel-iron alloycommonly known as permalloy with a few laminations of 75%v 21 3 nickel-iron-chromiumalloy.-

In this case the core consists of alternate laminations 1, cobalt-iron alloy of a composition in. the neighborhood of cobalt and 1 the balance iron and laminations 2 of'nickeliron alloy of about 7 8 nickel and the'balemployed for the cores although in such cases the relative number of laminations of the several materials may be varied.

What is claimed is:

1. inductance device having a core comprising laminations of iron-cobalt alloy of 40 to iron and the balance chiefly cobalt, iron-nickel alloy of- 40 to nickel and the balance chiefly iron, and iron-nickel alloy of 40 to 85% nickel containing 1% to 10% of a third element.

2. An inductance device such as set forth in claim 1 in which the iron-nickel alloy containing a third element is present in smaller quantity than the other alloys of the core.

' In witnesswhereof, I hereunto subscribe my name this 30th day of December, 1930. HORACE WHITTLE.

of service as a much larger core ance iron. The laminations 2 may consist-of silicon steel inst-ead'of nickel-iron alloywith satisfactory results for som'e purposes. containing nickel-iron alloy.

The invention is not restricted in its application to repeating coils but may be applied usefully to other transformers and other electromagnetic" devices in which it is desired to. increase the range of voltage or flux density for which the devices are highly and uniform} ly e'fiective.-"For example, a choke'coil having a magneticcore composedof combinations 0f materials herein described, willpossess high and fairly uniform impedance I over a wide range of applied voltages. In coils for filters orartificial lines where special propertiesare desired similar combinations 65 of two or three magnetic/materials may be The laminations 3 are composed of the chrominm- 

